Are higher doses of radiation in less time better than conventional radiotherapy for prostate cancer?

This study aimed to investigate whether dose-escalated hypo-fractionated (higher doses in less time) radiation therapy would lead to better overall survival or less chance of cancer recurrence than the conventional method. They found that there is superior cancer control associated with dose-escalated hypo-fractionated radiation therapy for prostate cancer.

A main treatment option for prostate cancer is radiation therapy. This involves the local use of high dose x-rays to kill tumor cells. Radiation therapy for the prostate is generally spread out over several weeks (up to 6-8) and takes place each weekday. The same dose of x-rays is delivered each day and conventionally this is 1.8Gy – 2Gy per day (Gy, or Gray, is the unit of measurement for radiation). Delivering more than 2Gy per daily dose spread out over less time is called dose escalation hypo-fractionation. 

It is thought that a higher dose can be delivered safely to the prostate using hypo-fractionated radiation therapy. This could lead to more effective treatment. Intensity-modulated radiation therapy (IMRT) is a radiation therapy technique which leads to a more accurate treatment. IMRT uses an advanced technique to make the radiation beam to take the shape of the tumor. This leads to less exposure to healthy surrounding tissues such as the rectum.

It is unclear if dose-escalated hypo-fractionated radiation therapy for prostate cancer is more effective than conventional radiation therapy.

This study included 206 patients with localized prostate cancer who were undergoing IMRT. They were randomly assigned to 75.6 Gy in 1.8 Gy fractions delivered over 8.4 weeks (conventional treatment) or 72 Gy in 2.4 Gy fractions delivered over 6 weeks (dose-escalated hypo-fractionated). They were followed up for an average of 8.5 years. Overall survival (patients still alive) and the risk of cancer recurrence were the main outcomes studied. 

The risk of cancer recurrence 8 years later was significantly lower in the hypo-fractioned group (10.7%) compared to the conventional group (15.4%). The 8-year overall survival was higher in the hypo-fractioned group (90%) than in the conventional treatment group (85.2%). 

There were more side-effects like constipation, diarrhea or rectal bleeding for those on dose-escalated hypo-fractionated treatment 12.6% as compared to 5.0% in the conventional treatment group.

This study found that there was better cancer control associated with dose-escalated hypo-fractionated radiation therapy for prostate cancer.

The findings regarding overall survival and risk of side effects in this study were not statistically significant. This means it was not a good level of evidence. Further studies are needed.